The present invention relates to semiconductor devices, and in particular relates to improving input/output circuit portions having output transistors for transmitting the output of an internal circuit to the outside.
In general, with semiconductor integrated circuits, input/output circuit portions for performing input and output between inside and outside circuits are arranged around semiconductor chips, and these input/output circuit portions have a plurality of electrode pads. A conventional configuration of an input/output circuit portion is explained below.
FIG. 2 is a circuit diagram of an input/output circuit portion. In FIG. 2, P1 denotes p-type MOS transistors whose sources are connected to a power line VDD. N1 denotes n-type MOS transistors whose sources are connected to a ground line VSS. The drains of the MOS transistors P1 and N1 are connected to one another, and those points of connection are connected to an electrode pad Pad. Each series circuit made of a p-type MOS transistor P1 and an n-type MOS transistor N1 constitutes an output transistor OT, and a plurality of groups (in FIG. 2, two groups) of output transistors OT are connected in parallel, forming an input/output cell IOC. The output transistors OT also serve as ESD (electro-static discharge) protection transistors of identical configurations.
FIG. 6 shows an example of an in-line configuration in which a plurality of input/output cells IOC, which are provided with the output transistors OT, are lined up in a single row and rectangular electrode pads Pad are disposed to the side of the input/output cells IOC. Each input/output IOC is connected to its own electrode pad Pad by wiring 60. The electrode pads Pad have substantially the same width as the width of the corresponding input/output cells IOC.
FIG. 7 shows another conventional input/output circuit portion. In FIG. 7, each rectangular electrode pad Pad is arranged above its input/output cell IOC. The electrode pads Pad are arranged more on the side opposite the internal circuit side (the right side in FIG. 7) of the input/output cells IOC than on its internal circuit side. Compared to the input/output circuit portion of FIG. 6, the input/output portion of FIG. 7 can be provided with a smaller area because the electrode pads Pad are not arranged to the side of the input/output cells IOC, thereby obviating the need for regions in which to dispose the electrode pads Pad and the wiring 60 for connecting the electrode pads Pad to the input/output circuit portions.
FIG. 8 shows the configuration of yet another conventional input/output circuit portion. With the input/output circuit portion of FIG. 8, the input/output cells IOC have been set to a narrow width in order to reduce the pitch. However, the fact that the wiring for connecting to the outside is bonded to the electrode pads Pad requires the width of the electrode pads Pad to be set wide enough that this bonding can be carried out favorably, and thus the width of the electrode pads Pad is wider than the width of the input/output cells IOC. Consequently, the electrode pads Pad cannot be arranged in a straight line like in FIG. 6, and are arranged in an overall staggered fashion, with the electrode pads Pad arranged alternately shifted to the left and right of one another.